1. Field of the Invention
The present invention relates to variable optical-property elements such as a variable focal-length lens, a variable focal-length diffraction optical element, a variable deflection-angle prism, and a deformable mirror, and to an optical apparatus such as spectacles, a video projector, a digital camera, a TV camera, an endoscope, a telescope, or a camera finder, having an optical system including such variable optical-property elements.
2. Description of Related Art
Conventional lenses have been manufactured by polishing glass. Since the lens itself cannot vary a focal length, a mechanical structure is complicated because a lens unit must be moved along the optical axis for focusing or zooming of a camera, or changing magnification.
Because a motor or the like is used for moving a part of the lens unit, this conventional practice has disadvantages that power consumption is large, noise is produced, response time is long, and much time is required for moving lenses.
For shake prevention as well, mechanical movement of the lenses by a motor or a solenoid causes defects such as a large power consumption and a complicate mechanical structure, resulting in a higher cost.
In a zoom imaging optical system such as a digital camera, the problem is raised that the position of an image on an imaging plane is considerably shifted, depending upon the focal position of reflected light, resulting in a change in a field direction.
Use of a prism of high refractive index causes inconvenience that aberration cannot be completely corrected.